The present invention relates to apparatus providing multiple ultrasonic sector image displays.
Ultrasonic scanning of regions of the human body has found wide application in recent years. A particular type of scanner used is a sector scanner since it has the ability to display a cross-sectional area of the human body. An ultrasonic sector scanner consists of a transducer or transducers and a means of steering the ultrasonic beam through a series of angles. The steering means can be either mechanical (moving the transducer(s)) or electronic (phased arrays) or a combination of the two. The transducer itself can be a single element or an arrangement of many elements which together form a beam. Multiple element transducers include linear phased arrays pulsed in groups, annular phased arrays, and two-dimensional matrix phased arrays.
In the preferred embodiment a mechanical sector scanner is used to produce the signals to be processed. In this scanner an ultrasonic transducer (a piezoelectric element) is mounted and motor driven through a suitable mechanical arrangement. The drive arrangement moves the transducer with an arc scanning motion. During this process, the transducer is pulsed with high voltage spikes at selected pulse repetition rates. The voltage spikes cause the piezoelectric element to mechanically ring thereby emitting very high frequency sound waves. These ultrasonic waves impinge upon the structure within the body, and when a difference of acoustic impedance exists, are partially reflected back to the transducer element. In the interval between pulses, the transducer element acts as a receiver. The reflected energy causes the transducer element to mechanically vibrate and the element generates an electrical signal. This signal is amplified and processed so that it can be displayed as a sector scan on a cathode ray tube.
In one approach, the mechanical driving arrangement not only drives the probe but also provides an electrical output analogous to transducer position by the use of position sensing means such as a potentiometer which translates position information into electrical energy. The electrical signal is processed and utilized to create horizontal and vertical signals which, along with the returning ultrasonic impulses, are used to create an X-Y display on the cathode ray tube. The resultant image is a representation of the internal organs of the body.
Scan displays on the cathode ray tube can be on the order of a 30.degree., 90.degree. or 120.degree. scan with a plurality of scan lines each beginning with the application of a pulse to the transducer and each field or scan representing the cross section scanned.
In order for the information displayed on the cathode ray tube monitor to be most effective in use, it is necessary to record these images so that they can later be viewed and compared. The scan image appearing on a cathode ray tube in real time is continuously changing, thereby making comparisons between images and/or measurements difficult.
In application to the field of cardiology, a desirable feature of ultrasonic scanning systems would be to provide a simultaneous display of successive frames of sector data acquired during the same cardiac cycle--for instance, the sector images occurring during early diastole, mid-diastole, late diastole, early systole, mid-systole, late systole.
One prior art approach for recording a sector image is to use an instant camera, which obviates the possibility of recording consecutive sector images (unless a multiframe camera is used). Another approach has been to use a movie camera or video tape recorder which provides closely spaced pictures.
In other prior art approaches, a strip chart recorder provides in hard copy form a readout of what is known as an intensity-modulated M-mode display. The recorder records on strip chart paper ultrasonic echo information as a function of time. Such strip chart readouts are particularly valuable in the study of motion patterns of moving structures within the heart.
It is desirable to provide apparatus for printing multiple sector images in hard copy form, such as those sector images occurring during one cardiac cycle, so that the attending physician can have at hand a "cardiac image profile" of sector data. Prior art systems have not had the capability of providing a hard copy of multiple sector scans taken closely spaced in time. Additionally, it is desirable to provide apparatus for displaying physiological parameters such as the electrocardiogram, phonocardiogram, blood pressure and pulse to further assist a physician in his anaylsis.
It would also be desirable to provide apparatus that could provide particular sector image displays on a cathode ray tube--a soft copy form of the display--thereby giving an attending physician the choice of selecting which images to output to the hard copy device.
Additionally, it would be desirable to incorporate digital techniques to enhance the sector image. One problem in the prior art occurs with the displaying of the scan lines themselves on a cathode ray tube along with the desired image information.
The appearance of the scan lines distracts the physician from the real information content of the image. A desirable objective would be to provide a digital processor which eliminates the appearance of noticeable scan lines.
In view of the above background, it is an object of the present invention to provide enhanced multiple-sector hard copy images of the heart and other body organs.